This invention relates to an optical disc reproducing apparatus for reproducing a so-called compact disc interactive (CD-I) on which the video information, such as picture or letter information, computer data, application programs etc., are recorded besides the audio information.
There is currently proposed a system, known as a CD-I system, in which video data, such as natural picture, RGB graphics, color lookup table graphics, animation etc., computer data, or application programs, abbreviated hereinafter to programs, are recorded on a compact disc, in addition to audio data, and in which a user may use these data interactively. Inasmuch as this CD-I system has the functions of reproducing the voice, letters or pictures, and executing program(s), and may be used in connection with AV devices for mainly audio and video information and electronic publication mainly of letter or character information, as well as educational or amusement devices, which rely upon program execution, it is thought to be a promising new type media system.
The CD-I system is made up of an optical disc on which audio data, video data or the like are recorded, referred to hereinafter as a CD-I disc, and a player for reproducing a CD-I disc, referred to hereinafter as a CD-I Player. Various specifications have been prescribed in connection with the CD-I system with a view to maintenance of interchangeability and extensive propagation for domestic use.
For example, in a CD-I disc, audio and video data, for which high accuracy is not a particular requirement, are recorded in accordance with a so-called form 2 of the CD-I data format, whilst computer data or programs, which are in need of error detection and correction, are recorded in accordance with a so-called form 1 of the CD-I data format.
With the CD-I system, four sound quality levels may be used, so that the audio data are processed with four-level data compression or coding, depending on the desired sound quality level, before being recorded on the CD-I disc. Thus the recorded data may be 16-bit PCM (Pulse Code Modulation) audio data for a conventional compact disc (PCM Audio Data), 8- or 4-bit ADPCM (Adaptive Differential Pulse Code Modulation) audio data, or so-called A-level, B-level or C-level audio data (ADPCM Audio Data).
On the other hand, four picture quality types, namely the picture quality for natural pictures, e.g. color photographs, that for RGB graphics, that for color lookup table graphics (CLUT graphics) and that for animation, may be used with the CD-I system, so that the video data are processed with data compression or encoding in accordance with the desired picture quality before being recorded on the CD-I disc. That is, with the picture quality for a natural picture, the video data are encoded with 8 bits per pixel and processed with non-interlaced DYUV encoding for recording. With the picture quality for RGB graphics, three color signals (RGB signals) for each pixel are encoded with 5 bits for encoding and, with the picture quality for CLUT graphics, the video data are recorded so that 256 colors may be displayed simultaneously by allocating 8 bits for each Pixel. Finally, with the picture quality for animation, the video data for the CLUT graphics are processed with data compression by the so-called run-length coding for recording.
A 68000 series microcomputer, which is a 16-bit CPU developed by MOTOROLLA Inc. is preferentially employed as a microcomputer making up a CD-I player (CPU). A so-called compact disc real-time operating system (CD-RTOS), corresponding to the existing OS-9, an operating system developed by MICROWEAR Inc. but added to by input/output managers and drivers for graphics/visual, pointer and audio processing operations, is preferentially employed as an operating system (OS), in consideration of program interchangeability and execution efficiency on the CD-I disc. In addition, and X-Y device, which may be accessed on the pixel-by-pixel basis, and a trigger button (for execute/stop), are preferentially employed as input devices. A compact disc (CD), on which only music has been recorded, may also be reproduced with the CD-I system.
It is noted that the disc on which only the PCM audio data are pre-recorded is termed a CD-DA disc, while the disc on which ADPCM audio data other than the PCM audio data, video data and the program(s) etc. are pre-recorded, is termed a CD-I disc and the disc on which the PCM audio data, ADPCM audio data, video data, programs etc. are pre-recorded, is termed a CD-I/CD-DA disc.
In the case of the CD-I disc and the CD-I/CD-DA disc, the mechanical sizes, such as the outside diameter, diameter of the central aperture or thickness, optical parameters, such as refractive index or reflectivity, recording parameters, such as the recording line density, track shape or track pitch, and the operating environment, are selected to be the same as those of the usual compact disc, that is the CD-DA disc.
The CD-I disc, the CD-I/CD-DA disc and the CD-DA disc may be distinguished from one another based on the table-of-contents (TOC) data.
That is, the PSEC information for POINT=A0 is [10] for the CD-I disc and the CD-I/CD-DA disc, whilst the PSEC information for POINT=A0 for the CD-DA disc is [00], so that the CD-I disc and the CD-I/CD-DA disc may be distinguished from the CD-DA disc based on the PSEC information for the POINT=A0. On the other hand, the control fields for POINT=A0, A1 and A2 for the CD-I disc are all [01X0], while the control field for POINT=A0 is [01X0] and the control field for POINT=A1 and A2 for the CD-I/CD-DA disc are [00X0], so that the CD-I disc may be distinguished from the CD-I/CD-DA disc based on the control field information for POINT=A1 and A2.
With, with the CD-I player, it is mandatory that various operations can be set by a pointing device including the X-Y device and a trigger button.
Since the setting operation by the pointing device is performed by picture display means for displaying a picture reproduced by the CD-I player, it is necessary with the conventional CD-I player to actuate the picture display means even when the CD-DA disc dedicated for music reproduction is to be reproduced. Besides, the contents of the picture displayed by the picture display means need to be checked, resulting in poor operability.
If, for overcoming the drawback, special operating means is provided for reproduction of the CD-DA disc, not only the degree of freedom in construction and designing is lowered due to the annexed operating means, but there arises the risk of mistaken operations.